150 psf LL for library stacks

[WWTEng]

Does this 150 psf include self weight of the stack or is it only for the contents of the stack? I always assumed that 150 was for the contents and stack self weight is separate.

 

[dik]

Might be a tad light... can get 400 psf for library areas...

Dik

 

[fegenbush]

If the stack is permanent, I would think it should be included in the dead load. If the stack is movable, I suppose it could be included in the live load, but I would probably bump the 150 psf up to be conservative. I can believe that actual live load (people) would be quite low for stack rooms.

 

[woodman88]

The lowest value for the weight of structural wood, in the NDS, is given as 25 pcf. Say the stacks are 1' deep and back to back. With a 2' space to walk between. To be able to reach the books when standing a 8' height of the stacks would be typical? So 8'(1'+1')25pcf/4'oc = 100 psf for the stacks of books. Now are your stacks higher and/or spaced closer and how much do your books weight? Now I would consider the stacks to run parallel to the joists. If so, be sure to design strongbacks to transfer the load to the adjacent joists if needed. As to whether the books are a live load or dead load, for the deflection calculations.
Interesting that the ASCE7-05 live loads do not address the library rooms and the 2009 IBC gives a 90" (7.5') high and 3' walking space between (for a 5' oc spacing) as a requirement of their 150 psf live load.

Garth Dreger PE - AZ Phoenix area
As EOR's we should take the responsibility to design our structures to support the components we allow in our design per that industry standards.

 

[IsaacStructural]

woodman88 are you using 25pcf as an estimate of paper density? that actually seems quite low to me.

M.S. Structural Engineering
Licensed Structural Engineer and Licensed Professional Engineer (Illinois)

 

[woodman88]

IsaacStructural - Not "paper density" but book density. In any case, my example was meant to show IMHO that the 150 psf live load in the IBC includes the weight of the book stacks. I would find it hard to justify a higher live (or to use the books as a dead load) load for a typical library room. Now I might/would/try to increase the load anyway.

Garth Dreger PE - AZ Phoenix area
As EOR's we should take the responsibility to design our structures to support the components we allow in our design per that industry standards.

 

[dik]

I've done library stack areas where the cases are on rollers to eliminate the walking space... you have to determine the maximum loading based on the use of the area.

Dik

 

[WWTEng]

This question pertains to an existing job, where we are possibly thinking of sharpening the pencil to get a little extra load capacity.

On my last library project, I did some research and 150 psf turned out to be a little conservative actually although I used 170. The most common book type is Octavo (6"x9"). Paper density is 50 pcf for your average print paper (a little lower actually) but instead of octavo lets use quarto (12"x9.5"). Now for a 90"x12" stack the paper weight: 9.5" widex90" tall(conservative since books are hardly ever stacked full height)x50 pcf=300 psf. With 36" space between the stacks, the 150 psf live load works out just about. And I also included actual weight of the stack itself as DL.

 

[wannabeSE]

WWTEng,
Have you looked at the commentary to chapter 4 of ASCE 7-05? It contains information on library stack rooms including some of the the assumptions used to justify the 150psf loading. Concerning the weight of the stacks themselves,the commentary states: "Book stack weights also vary, but not by enough to significantly affect the overall loading."